Interactive system and method for integral emergency unlocking of a locked cockpit door on an airplane

ABSTRACT

An interactive system for unlocking a locked airplane cockpit door having at least one ground station and at least one system for transmitting data between the ground station and airplane, including a ground station signal for actuating a door unlock mechanism. The airplane has: a passenger cabin located door unlock request unit to generate a door unlock request signal; a unit to transmit the request signal; at least one image capture unit in the passenger cabin or a cockpit and a unit to transmit images; a unit for receiving a door unlock signal; and an on-board computer, configured to receive the door unlock signal from the receiving unit and activate the door unlock mechanism. The ground station is connected to at least one receiving station for door unlock request and image signals transmitted from airplanes and is provided with or connected to a transmitting unit for door unlock signals.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the German patent application No.10 2015 012 173.1 filed on Sep. 23, 2015, the entire disclosures ofwhich are incorporated herein by way of reference.

TECHNICAL FIELD

The present invention relates to an interactive system for integralemergency unlocking of a locked cockpit door of an airplane. It alsorelates to a method for integral emergency unlocking of a locked cockpitdoor on an airplane. The interactive system according to the inventionis designed and provided in particular for carrying out the methodaccording to the invention.

BACKGROUND OF THE INVENTION

For safety reasons and in particular to protect the pilot from attacksfrom the area of the passenger cabin, the cockpit door between thepassenger cabin and the cockpit is designed to be unbreakable andbulletproof and can be opened only from the cockpit side during flight.There is the option of sending an open request from the passenger cabinto the cockpit, but if the cockpit crew does not or cannot respond tothis request, then it is impossible for anyone to access the cockpitfrom the passenger cabin in an emergency. The scenario on which theinvention is based is thus that an authorized crew member of theairplane is standing in front of the locked cockpit door and cannot openit in the traditional way, i.e., the authorized crew member is preventedor denied access to the cockpit without adequate reason. The authorizedcrew member thus has the well-founded suspicion that an emergency or acriminal act is underway.

The interactive system and method according to the invention shouldserve to allow opening of a locked cockpit door of an airplane in flightin an emergency, even from outside the cockpit, although only by anauthorized person, and this is possible even if the pilot is currentlydenying access to the cockpit or cannot grant access because of a healthimpairment.

It is known from DE 101 45 261 A1 that a cockpit door can be opened bymeans of a radio signal, preferably encrypted, from air traffic controlor air navigation services.

It is known from DE 197 32 806 A1 that the passenger cabin can bemonitored from the cockpit by means of video cameras. The image datafrom these monitoring cameras can also be transferred automatically to aground station, for example, an air control tower, in certainsituations.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a generic interactivesystem and a generic method for unlocking a locked cockpit door on anairplane that will make it possible in an emergency to unlock and openthe cockpit door from the passenger cabin of the airplane withoutthereby endangering the safety of the cockpit crew in the event of thepresence of potential airplane hijackers in the passenger cabin. Thismeans that, in the latter case, unlocking by the interactive systemand/or the method must be precluded.

The interactive system according to the invention for unlocking a lockedcockpit door of an airplane comprises at least one ground station and atleast one data transmission system between the ground station and atleast one airplane, such that a signal can be transmitted from theground station to the airplane for activation of a door unlock mechanismfor the cockpit door. The airplane has a door unlock request unit, whichis provided in the passenger cabin of the airplane for generating a doorunlock request signal and a signal transmitting unit for the door unlockrequest signal. Furthermore, the airplane is equipped with at least oneimage capture unit in the passenger cabin and/or in the cockpit of theairplane and an image transmitting unit for transmitting detected imagesto the ground station. In addition, the airplane has a receiving unitfor receiving a door unlock signal and an on-board computer designed toreceive the door unlock signal from the receiving unit and to activatethe door unlock mechanism of the cockpit door. The at least one groundstation is provided with or connected to at least one receiving stationfor door unlock request signals and image signals emitted by airplaneand provided with or connected to at least one transmitting unit fordoor unlock signals.

This interactive system according to the invention makes it possible toreliably and safely open a locked cockpit door in an airplane in anemergency from outside of the cockpit by authorized persons and onlysuch persons even if the current airplane pilot is refusing to grantaccess or cannot grant access for health reasons.

The door unlock request unit, the signal transmitting unit, the at leastone image capture unit, the image transmitting unit, the receiving unitfor receiving a door unlock signal, the on-board computer responsiblefor unlocking the cockpit door and the door unlock mechanism arepreferably designed so that they cannot be switched off or at leastcannot be switched off from the cockpit.

In a preferred refinement of the invention, the data transmission systemhas a satellite network between the ground station and the airplane.

It is also advantageous if the data transmission system between theground station and the airplane is autonomous and independent of othercommunications equipment between the airplane and ground.

A particularly preferred specific embodiment of the interactive systemaccording to the invention is characterized in that the door unlockrequest unit has an input device for inputting a personal authenticationkey into the on-board computer of the airplane responsible for unlockingthe cockpit door; the on-board computer responsible for unlocking thecockpit door is designed to authenticate a received signed door unlocksignal; and the at least one ground station is equipped with averification unit for the received door unlock request signals and witha generating and signature unit for door unlock signals.

This method according to the invention for unlocking a locked cockpitdoor of an airplane, wherein the cockpit door delineating the cockpitfrom the passenger cabin is unlocked on the basis of an unlock signalemitted by a ground station, comprises the following steps:

a) Inputting a personal authentication key comprising a passphrase and asecret key into an input device in the passenger cabin by means of afirst crew member of the airplane crew, wherein the authentication keythat has been input is sent to an on-board computer of the airplane,which is responsible for unlocking the cockpit door, and whereby animage transfer command is triggered;

b) Transmitting the recorded images and/or live images recorded or beingrecorded by at least one image capture unit in the passenger cabinand/or in the cockpit of the airplane to a ground station;

c) Transmitting a door unlock request signal containing a personalidentification code of the first crew member from the passenger cabin tothe ground station;

d) Verifying the personal identification code, the transmitted imagesand flight information data in the ground station for deviations fromtarget values;

e) If no deviations from target values are found, generating anauthenticated door unlock signal using a public key stored in a memoryin the ground station for the first crew member and a secret key of theground station as signatures for the door unlock signal;

f) Sending the signed door unlock signal from the ground station to theairplane and receiving the signed door unlock signal by a receiver ofthe airplane;

g) Forwarding the signed door unlock signal from the receiver in theairplane to the on-board computer responsible for unlocking the cockpitdoor in the airplane;

h) Verifying the signatures of the signed door unlock signal, namely

using the secret key of the first crew member with the personalauthentication key input in step a), and

using the public key of the ground station stored on board the airplane;

i) Unlocking and opening the cockpit door, unless or as long asverification of the signatures of the door unlock signal has notrevealed an error;

Due to the sequence of the method steps according to the invention andproviding authentications, the cockpit door can be unlocked and openedonly by authorized personnel and only in an emergency confirmed andverified by the ground station. This makes it possible to reliablycounteract a health-related unavailability of the pilot or anintentional criminal act by a crew member or even hijacking of anairplane due to seizure of the cockpit by non-crew members. Aninteractive system according to the invention implementing the methodaccording to the invention fulfills very high demands regarding theavailability as well as the integrity and the required safety.

Preferably, a personal authentication key must be entered additionallyin step a) by at least one additional crew member of the airplane crew,wherein the personal identification code of the additional crew memberis also transmitted in step c) from the passenger cabin to the groundstation, wherein the signed door unlock signal is generated in step e)also using the authentication key of the additional crew member andwherein the personal authentication key of the additional crew member isalso verified in step h). This further increases the security of theentire process.

In step d) the ground station preferably additionally makes a verbalquery of the current pilot of the airplane for status information.

It is also advantageous if the signed door unlock signal is sent fromthe ground station in step f) as a radio signal at a standardizedfrequency, so that the signed door unlock signal is received by allairplanes in the reception area equipped with a suitable receiver.

Preferred exemplary embodiments of the invention with additional designdetails and additional advantages are described and explained in greaterdetail below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of the interactive system according tothe invention, and

FIG. 2 shows a usage diagram of an interactive system according to theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows schematically a detail of an airplane 1 having a cockpit Cand a passenger cabin P, separated from one another by a cockpit door10. The cockpit door 10 can be opened only from the cockpit side duringflight operation.

A door unlock request unit 12 for generating a door unlock requestsignal is provided in the passenger cabin P. The door unlock requestunit is therefore equipped with an input device 12′ for inputting apersonal authentication key of a crew member operating the input deviceand thereby making an emergency call.

This personal identification key may be stored on a chip card or on asuitable RFID transponder, which could even be implanted. Each crewmember of the airplane 1 or a suitable subset of the airplane crew canbe equipped with such an individual personal authentication key. Thechip card or the RFID transponder contains the secret personalauthentication key (SK-1) for decryption; this secret key is saved usinga passphrase. One example of such a key is a so-called “secret key”according to the known principle of the public key method. Since such apersonal authentication key is person-specific, it contains or forms atthe same time a personal identification code of the owner of the key. Inthis case, the input device 12′ may be designed as or may include areader, preferably an almost indestructible reader for correspondingchip cards or RFID transponders.

The input personal authentication key is forwarded by the input device12′ to an on-board computer 19 of the airplane 1, which is responsiblefor unlocking the cockpit door 10. For this purpose, the on-boardcomputer 19 responsible for unlocking the cockpit door 10 is connectedto a door unlock mechanism 11 of the cockpit door 10. The door unlockrequest device 12 is also connected to a signaling unit 13 of theairplane 1 in order to forward a door unlock request signal a, triggeredby input of the personal authentication key and the activation of theinput device to the signal sending unit 13 for transmission to a groundstation 2. The door unlock request signal a is sent to a ground stationfrom there.

An image capture unit 14, which is formed by a video camera, forexample, is provided in the passenger cabin P and detects the space infront of the cockpit door 10. Additional image capture units (not shown)may also be provided. The image signal detected by the image capturedevice 14 (and optionally by the additional image capture devices) issent to an image transmitting unit 16 of the airplane 1. At least oneimage capture unit 15 is also provided in the cockpit C, its imagesignal also being sent to the image transmitting unit 16 fortransmission to the ground station 2. The image capture devices 14, 15may be cameras for monitoring the passenger cabin and the cockpit or mayinclude such cameras that are equipped with or connected to memory mediaon board the airplane and that record continuously. The recorded imagematerial is stored for a predefinable period of time before it can beoverwritten. This makes it possible to also transmit the stored imagedata from the past to the ground station 2. After input of the personalauthentication key and confirmation of the input device, the saved andcurrent image signals b are automatically sent from the imagetransmitting unit 16 to the ground station 2.

The design and functioning of the interactive system according to theinvention will now be described with reference to the diagram in FIG. 2.

The ground station 2 has a network of receiving stations, preferably aglobal network, only one receiving station 20 of which is illustrated inFIG. 2. The signals (door unlock request signal a and image signals b)received by the receiving station 20 are forwarded to a command central21 at the ground station 2.

The door unlock request signal a and at least one image signal b arethus sent to the receiving station 20 of ground station 2 by theairplane 1 triggering the emergency call. This signal transmission cantake place, for example, over a shortwave transmitter-receiver system,which is either independent of the aeronautical radio hardware orutilizes the aeronautical radio hardware. These signals may beencrypted, but encryption is not absolutely necessary for thistransmission.

The received door unlock request signal a is analyzed in command central21, and the personal identification code of the crew member that hastriggered the door unlock request contained therein is verified at leastfor whether this identification code is valid and belongs to a currentcrew member of the airplane 1. In the case of the public key method, therespective so-called “public key,” called PK-1 here, is used for thispurpose. In addition, the images of the received image signals arechecked for whether there are any detectable irregularities in thecockpit C and/or in the passenger cabin P (for example, a threat to acrew member) that might prevent opening of the cockpit door 10. Inaddition, generally available flight information data is checked forwhether the airplane 1 is deviating or has already deviated from theintended course for the intended flight altitude.

If no suspicious events that would prevent the door from being unlockedare detected on board the airplane 1 in command center 21, then a doorunlock signal c is generated and sent over a transmitting unit 22connected to the ground station 2 or belonging to the ground station 2and part of a preferably global network of transmitting units. Then thedoor unlock signal c is emitted by this transmitting unit 22 (or by aplurality of transmitting units of the network) and can be received bythe receiving unit 17 of the airplane 1. In the example shown here, thedoor unlock signal c here is transmitted by the transmitting unit 22over a network of satellites 31, 32, from whence the door unlock signalc is sent to all airplanes 1, 1′ that are within the receiving range ofthe transmitters 31′, 32′ of the satellites 31, 32. In order for thedoor unlock signal c to manifest an effect only in the airplane 1 fromwhich the emergency call was sent, it is provided that signal c isauthenticated as described below.

Executable software is stored on a computer in ground station 2,generating an authenticated door unlock signal c. To do so, the knownpublic key (PK-1) of the crew member sending the emergency call is usedon board the airplane 1 to limit the door unlock signal c to thisairplane 1. In addition, a secret key (SK-2) assigned to ground station2 is used for authentication to generate the authenticated door unlocksignal c. The public keys (PK-2) belonging to the secret keys (SK-2) ofall ground stations 2 belonging to the interactive system according tothe invention are stored in a memory assigned to the respective on-boardcomputer 19 of the airplanes 1, 1′ participating in the interactivesystem according to the invention.

Consequently, a system of satellites 31, 32, including the respectiverelay stations for the uplink (transmitting units 22), possiblysupplemented by additional transmitting stations (not shown) on theground will receive the authenticated door unlock signal c from anauthorized command central 21, this signal then being emitted withsufficient frequency at least within the reception area of the airplane1. The requests to this satellite system include, among other things avery high availability and a very high assurance of authenticity of themessages transmitted (integrity request). For example, it may be aglobal navigation system (GNSS system), such as the Galileo system usingthe ERIS channel or a satellite-based navigation supplement system (SBASsystem) using one of the message types 8, 11, 13 to 16 or 19 to 23reserved for future applications or corresponding message types providedfor the current L5-SBAS.

The receiving units 17 of the airplanes 1, 1′ participating in theinteractive system according to the invention are equipped with areceiver, which receives the signal emitted by the satellites 31, 32 andoptionally also emitted by transmitting stations on the ground andforwarded to the on-board computer 19 responsible for the cockpit door10. In the case of the Galileo system, the receiver may be anERIS-capable Galileo receiver, for example, which can process the doorunlock signal c. In an SBAS system, the receiver may be an SBASreceiver, for example, which can process the received message containingthe door unlock signal c.

Executable software is stored in the on-board computer 19, verifying thevalidity and authenticity of the received door unlock signal in theon-board computer 19 on the basis of the personal key (SK-1) loaded andthe stored public key (PK-2) of the ground station 2 and then unlockingand opening the cockpit door 10 if the validity and authenticity of thekeys are verified.

The public keys (PK-1) of all crew members of the airplanes 1, 1′connected to the emergency system according to the invention togetherwith their identification codes for unambiguous identification of thepersons are stored in at least one memory unit of the ground station 2.Information about the at least one command central 21 of the groundstation 2 is thus either known to them or can be made known to them atany time within a sufficiently short period of time.

The request of a door unlock request signal preferably takes place withthe steps described below:

A first and optionally an additional crew member will load theirrespective personal (secret) keys (SK-1) into the on-board computer 19that is relevant for the cockpit door by entering their respectivepassphrase via the reader of the input device 12′. These persons areregarded as the initiators of the emergency call. Loading a personal keyinto the on-board computer 19 also leads to automatic encryptedtransmission of the images, recorded by the image capture units 14, 15,of the passenger cabin monitoring and the cockpit monitoring to thereceiving stations 20 of the ground station 2. After preprocessing,these stations forward the information to the command central 21.

In addition, the door unlock request signal and the personnelidentification code of the (respective) initiator of the emergency callare transmitted to ground station 2. This can take place automaticallyor via voice radio. For example, one crew member of airplane 1 contactsthe ground station 2 on an intended communication link. In doing so, allthe initiators are specified and the door unlock procedure is initiated.

The command central 21 of the ground station carries out suitablemeasures for verifying the legal validity and for justifying the doorunlock request, for example:

(a) Analysis of the image material of the cabin and cockpit monitoringto rule out or detect any foreign influences, so that, for example, acoerced door unlock request can be detected;

(b) Observing the flight path of the airplane to detect anyirregularities;

(c) Calling the current airplane pilot to explain the reason forrefusing cockpit access.

These measures for verifying the legality and justification of the doorunlock request can also be carried out automatically.

If the verification does not reveal any irregularities, i.e., nodeviations from the target values, then an authenticated door unlocksignal c is generated, which may be initiated automatically or manually.The authorized personnel in command central 21, for example, initiatesthis generation of the authenticated door unlock signal c. In doing so,the public keys (PK-1) of all initiators on board the airplane 1 and thesecret keys (SK-2) of the ground station are used for the authenticationof the door unlock signal c.

This authenticated door unlock signal c is sent to the correspondingrelay stations such as the transmitting unit 22 for the uplink, whichthen transmits it to the corresponding satellite(s) 31, 32 of thesatellite system. From there, it is often distributed adequately.

The respective receivers in the receiving units 17 of all airplanes 1,1′ in the reception area belonging to the interactive system accordingto the invention will receive the authenticated door unlock signal c andforward it to the respective on-board computer 19 assigned to thecockpit door 10. The on-board computer 19 will attempt to verify thedoor unlock signal. However, only the on-board computer 19 of theairplane 1 from which the emergency call has been transmitted is capableof doing so, because that computer knows the personal keys of theinitiators required for decryption. Through the verified signature ofthe door unlock signal, the integrity of the door unlock command isensured. It is therefore certain that the door being unlocked is thecockpit door in the correct airplane 1. The integrity of the door unlockrequest is supported by the required input of the passphrase of at leastone crew member and by other measures taken in the ground station 2,such as, for example, the exclusion of foreign influences, observationof a flight path that deviates from the intended flight path filed byground station or the lack of response of the current airplane pilot topersonal calls from the ground station 2.

In summary, the interactive system according to the invention forms asecurity system, which has the result that a locked cockpit door on anairplane can be opened in an emergency from outside of the cockpit byauthorized persons or devices, even if the current airplane pilot cannotgrant access or has actively refused access. This opening of the doorcan be performed only by authorized personnel and only in a confirmedemergency. Thus, both an intended criminal act on the part of a crewmember as well as hijacking of the airplane by seizure of the cockpit bya non-crew member can be counteracted reliably. The overall systemproposed to solve this problem meets very high demands regardingavailability and integrity.

Reference numerals in the description and drawings serve only to improvean understanding of the invention and should not restrict the scope ofprotection.

While at least one exemplary embodiment of the present invention(s) isdisclosed herein, it should be understood that modifications,substitutions and alternatives may be apparent to one of ordinary skillin the art and can be made without departing from the scope of thisdisclosure. This disclosure is intended to cover any adaptations orvariations of the exemplary embodiment(s). In addition, in thisdisclosure, the terms “comprise” or “comprising” do not exclude otherelements or steps, the terms “a” or “one” do not exclude a pluralnumber, and the term “or” means either or both. Furthermore,characteristics or steps which have been described may also be used incombination with other characteristics or steps and in any order unlessthe disclosure or context suggests otherwise. This disclosure herebyincorporates by reference the complete disclosure of any patent orapplication from which it claims benefit or priority.

LIST OF REFERENCE NUMERALS

They denote:

1 airplane

1′ airplane

2 ground station

3 data transmission system

10 cockpit door

11 door unlock mechanism

12 request device

12′ input device

13 signal transmitting unit

14 image capture unit

15 image capture unit

16 image transmitting unit

17 receiving unit

19 on-board computer

20 receiving station

21 command central

22 transmitting unit

30 satellite network

31 satellite

31′ transmitter

32 satellite

32′ transmitter

C cockpit

P passenger cabin

a door unlock request signal

b image signal

c door unlock signal

The invention claimed is:
 1. An interactive system for unlocking alocked cockpit door of an airplane, the interactive system comprising:at least one ground station, and at least one data transmission systemfor transmitting data between a ground station and the airplane, whereina signal for actuating a door unlock mechanism of the cockpit door canbe transmitted from the ground station to the airplane, an on-boardcomputer in the airplane; a door unlock request unit provided in apassenger cabin of the airplane to generate a door unlock requestsignal, the door unlock request unit having an input device configuredfor a crew member, who has a public encryption key, to sign a doorunlock request; a signal transmitting unit for the door unlock requestsignal in the airplane; at least one image capture unit in at least oneof the passenger cabin and a cockpit of the airplane and an imagetransmitting unit in the airplane for transmitting detected images tothe ground station; a receiving unit for receiving a door unlock signalin the airplane from the at least one ground station; the on-boardcomputer in the airplane being configured to receive the door unlocksignal from the receiving unit, and to activate the door unlockmechanism of the cockpit door; the at least one ground station beingconnected to at least one receiving station for door unlock requestsignals and image signals emitted by airplanes, the at least one groundstation being equipped with a generating and signature unit for doorunlock signals that utilizes a secret key of the ground station and thepublic key of the crew member initiating the unlock request to encryptthe door unlock signal, and the at least one ground station beingprovided with or connected to at least one transmitting unit forencrypted door unlock signals.
 2. The interactive system according toclaim 1, wherein the door unlock request unit, the signals transmittingunit, the at least one image capture unit, the image transmitting unit,the receiving unit for receiving a door unlock signal, the on-boardcomputer responsible for unlocking the cockpit door and the door unlockmechanism cannot be turned off from the cockpit.
 3. The interactivesystem according to claim 1, wherein the door unlock request unit, thesignals transmitting unit, the at least one image capture unit, theimage transmitting unit, the receiving unit for receiving a door unlocksignal, the on-board computer responsible for unlocking the cockpit doorand the door unlock mechanism cannot be turned off.
 4. The interactivesystem according to claim 1, wherein the data transmission systemincludes a satellite network between the ground station and theairplane.
 5. The interactive system according to claim 1, wherein thedata transmission system is autonomous and independent, between theground station and the airplane, of other communications equipmentbetween the airplane and the ground.
 6. The interactive system accordingto claim 1, wherein the door unlock request unit includes an inputdevice for input of a personal authentication key into the on-boardcomputer of the airplane responsible for unlocking the cockpit door; theon-board computer that is responsible for unlocking the cockpit door isconfigured to authenticate a received signed door unlock signal, and theat least one ground station is equipped with a verification unit for thereceived door unlock request signals and with a generation and signatureunit for the door unlock signals.
 7. A method for unlocking a lockedcockpit door of an airplane with an interactive system, wherein thecockpit door, delineating a cockpit from a passenger cabin, is unlockedon the basis of an unlock signal emitted by a ground station, comprisingthe following steps: a) receiving, by the system, the input of apersonal authentication key of a first crew member of the airplane crew,comprising a secret key and a passphrase for securing the secret key,into an input device in the passenger cabin by a first crew member ofthe airplane crew, wherein the personal authentication key that is inputis sent to an on-board computer of the airplane, which is responsiblefor unlocking the cockpit door, thereby triggering an image transmissioncommand; b) transmitting, by the system, recorded images and/or liveimages that are being or have been recorded by at least one imagecapture unit in the passenger cabin and/or in the cockpit of theairplane to a ground station; c) transmitting, by the system, a doorunlock request signal and a personal identification code of the firstcrew member from the passenger cabin to the ground station; d)verifying, by the system, the personal identification code, thetransmitted images and flight information data in the ground station fordeviations; e) if no deviations are found, generating, by the system, anauthenticated door unlock signal using a public key of the first crewmember stored in a memory of the ground station and a secret key of theground station as signatures for the door unlock signal; f) sending, bythe system, the signed door unlock signal from the ground station to theairplane and receiving the signed door unlock signal by a receiver ofthe airplane; g) forwarding, by the system, the signed door unlocksignal from the receiver on the airplane and to the on-board computer ofthe airplane responsible for unlocking the cockpit door; h) verifying,by the system, the signatures of the signed door unlock signal, namelyusing the secret key of the first crew member, and using a public key ofthe ground station stored on board the airplane; i) unlocking andopening the cockpit door, by the system, as long as verification ofsignatures of the door unlock signal has not revealed any errors.
 8. Themethod according to claim 7, wherein the receiving of the input of apersonal authentication key into the input device in step a) mustadditionally include the receiving of the input of a personalauthentication key by at least one additional crew member of theairplane crew; in step c), a personal identification code of theadditional crew member is transmitted, by the system, from the passengercabin to the ground station; the generation of the signed door unlocksignal in step e) takes place, by the system, by also using a public keyof the additional crew member; and in step h) the personalauthentication key of the additional crew member is also verified, bythe system.
 9. The method according to claim 7, wherein, in step d) averbal query of the status information from the actual airplane pilot ofthe airplane is additionally carried out from the ground station. 10.The method according to claim 7, wherein the transmission of the signeddoor unlock signal from the ground station, by the system, in step f)takes place at a standardized frequency as a radio signal so that thesigned door unlock signal is received by all airplanes that are in thereception area and are equipped with a suitable receiver.
 11. Aninteractive system for unlocking a locked cockpit door of an airplane,the interactive system comprising: at least one ground station, and atleast one data transmission system for transmitting data between aground station and the airplane, wherein a signal for actuating a doorunlock mechanism of the cockpit door can be transmitted from the groundstation to the airplane, an on-board computer in the airplane; a doorunlock request unit provided in a passenger cabin of the airplane togenerate a door unlock request signal, the door unlock request unithaving an input device configured for a crew member to sign a doorunlock request by using a personal identification code; a signaltransmitting unit for the door unlock request signal and crew memberpersonal identification code in the airplane; at least one image captureunit in at least one of the passenger cabin and a cockpit of theairplane and an image transmitting unit in the airplane for transmittingdetected images to the ground station; a receiving unit for receiving adoor unlock signal in the airplane from the at least one ground station;the on-board computer in the airplane being configured to receive thedoor unlock signal from the receiving unit, and to activate the doorunlock mechanism of the cockpit door; the at least one ground stationbeing connected to at least one receiving station for door unlockrequest signals, crew member personal identification codes, and imagesignals emitted by airplanes, the at least one ground station beingequipped with a verification unit for the received crew member personalidentification code to verify that the personal identification codebelongs to a current crew member of the airplane, and with a generatingunit for door unlock signals, and the at least one ground station beingprovided with or connected to at least one transmitting unit for doorunlock signals.
 12. The interactive system according to claim 1, whereinthe door unlock request input device is configured for a crew member tosign a door unlock request by using a personal identification code, thesignal transmitting unit for the door unlock request signal is alsoconfigured to transmit the crew member personal identification code, andthe at least one ground station is equipped with a verification unit forthe received crew member personal identification code to verify that thepersonal identification code belongs to a current crew member of theairplane.
 13. The interactive system according to claim 1, wherein theat least one ground station is configured to verify flight informationdata for deviations from predetermined flight information.
 14. Theinteractive system according to claim 11, wherein the at least oneground station is configured to verify flight information data fordeviations from predetermined flight information.